The present invention generally relates to sewage treatment and specifically to septage, holding tank waste and landfill leachate treatment which cannot be accommodated by typical municipal-type waste treatment facilities.
The Environmental Protection Agency (EPA) and state governments dictate the discharge standards for municipal-type waste treatment facilities. A standard unit of measure used is the biological oxygen demand loading concentration (BOD) given in parts per million (ppm). In Michigan for example, the BOD for the prevalent secondary municipal-type waste treatment facility discharge is limited to 20 to 30 ppm. This mandates a BOD less than 250 ppm in the sanitary sewer supplying the municipal-type waste treatment facility in order to avoid overloading and shocking the treatment facility system.
Waste treatment facilities are designed to accommodate specified volumes of waste at a specified BOD. The mandated BOD maximum of 250 ppm will typically accommodate a residential sanitary sewer system at volumes which do not exceed the design capacity of the municipal-type waste treatment facility. However, municipal-type waste treatment facilities are being pushed to their capabilities as communities grow. In view of this stress, the municipal-type waste treatment facility cannot practically accommodate sources of high concentration waste. These sources of high concentration waste include landfill leachate, septage and holding tank waste.
Leachate and septage are too concentrated for typical municipal-type waste treatment facility processing.
Leachate typically has a BOD of about 5,000 ppm. Septage typically has a BOD of about 3,500 ppm. Holding tank waste presents a different problem of excessive amounts of solid waste, typically up to 40%. A common method of disposal for these high concentration wastes is to simply spread the waste over an open field or farm field. This presents other problems. First, nitrates, common in this waste, quickly filter through the ground, settling into the ground water and presenting a potential ground water pollution problem. Second, even if buried or cultivated into the soil through normal farming activity, solid wastes have a tendency to float up through and surface above the ground. Finally, monitoring and regulating the disposal of heavy metal and toxic wastes is quite difficult with significant ground and water pollution problems resulting.